1. Field of the Invention
This invention relates generally to a semiconductor integrated circuit and more particularly to such a circuit in which an island region is electrically isolated through a dielectric layer, and to a method for manufacturing the same.
2. Description of the Prior Art
Semiconductor integrated circuits in which electrical insulation is provided between semiconductor elements using a dielectric layer are conventionally known. A plurality of semiconductor elements in the integrated circuit are arranged at a predetermined interval on one side of a semiconductor polycrystalline layer, and a dielectric or insulator separation layer is formed so as to insulate the semiconductor elements from the polycrystalline layer. Such integrated circuits are suitable for high power purposes.
However, such integrated circuits manufactured by well known prior art processes have some drawbacks, one of which is in the difficulty of manufacturing them. For example, in the process where a polycrystalline layer is formed by gas phase growth, at first the size of the polycrystalline particle is small; however, it becomes larger and larger with the advance of polycrystalline growth which causes warping of the semiconductor substrate owing to the difference in the expansion coefficient of the polycrystalline layer as a function of depth. Furthermore, warping is similarly caused due to the difference in expansion coefficient between the polycrystalline layer and the monocrystalline layer in which the semiconductor element is formed. The above-mentioned warping of the semiconductor substrate is difficult to eliminate, making the subsequent photoetching process difficult. Furthermore, with the prior art method it is very difficult to lap the polycrystalline layer to a uniform thickness.
For these reasons the prior art method, as described above, is unsuitable for manufacturing semiconductor integrated circuits. A need therefore exists for the present invention which overcomes the problems arising from the processing sequence of the prior art wherein the polycrystalline layer is grown from the gas phase.